An ultrasound diagnostic apparatus transmits an ultrasonic pulse to a biological body and receives a reflected wave thereof to apply the principle of pulse reflection to the reflected wave thus received, thereby generating an image of biological tissues. The ultrasound diagnostic apparatus has characteristics such as non-invasive and real-time display and is widely used in prenatal checkups.
Operators who do not have enough experience of radiogram interpretation find it difficult to grasp the position and the orientation of a fetus in a mother from an ultrasonic image displayed on a display (hereinafter, an echo image as appropriate). As a fetus grows large in late pregnancy, it becomes further difficult for operators who do not have enough experience of radiogram interpretation to grasp the position and the orientation of the fetus because its head and abdomen are partially displayed in one screen of the echo image. However, there are demands from pregnant women for grasping the position and the orientation of fetuses.